In a semiconductor device manufacturing process, wiring processing is performed. A damascene method is known as one of the wiring process techniques. In the damascene method, a barrier film is formed on a surface of an insulating film where a recess is formed. The barrier film is generally made of tantalum, tantalum nitride, cobalt or ruthenium. Then, a copper film is formed on the barrier film. The copper film is formed by, e.g., a sputtering method.
In Japanese Patent Application Publication No. H11-343570, there is disclosed a method for forming a copper film by sputtering, wherein a temperature of a target object having an insulating film is set to a low level of 20° C. or less. In the method disclosed in Japanese Patent Application Publication No. H11-343570, by performing the sputtering of copper in a state where the temperature of the target object is set to a low level, agglomeration of copper is suppressed and a copper film has a flat surface.
A wiring made of copper requires low resistance. However, when a crystal in the copper film has a small particle size, the resistance of the wiring made of copper is increased. Therefore, it is required to form a copper film having low resistance.